Thanks for taking a little time to answer me.
The answer, however, leave me rather unsatisfied.
First of all, nothing has changed with the latest versions. The problem is not specific to a particular module, neither stable nor beta.
The 3 Affinity modules feature pdf support, with no apparent restriction. I do not have the Illustrator / InDesign “reference softwares” but:
- Since the "little" Photoshop Elements (version 11 or 2020) opens it correctly, it seems to me that Affinity Photo should be able to open it
- Since Inkscape opens it correctly, Affinity Designer should be able to open it correctly.
- Likewise, since Scribus opens it correctly too, Affinity Publisher should be able to too.
If I start to think to myself that in a PDF that I open, some elements may not appear, it bothers me, I don't care if tenors don’t do better.
The problem is not reduced to the red square. Ditto with a barcode also created with PDF-XChange PRO 9.
I add that when I open my file in Inkscape and copy the offending elements there, I can paste them onto the blank Affinity pages without any problem.
That said, that doesn't take away from the tremendous work of the developers.
Red square + Barcode.pdf